When an object moves in an image displayed on a screen of a display device, a moving direction of the object is taken into account to make an aspect ratio or the like be symmetrical with regard to the up, down, left and right sides of the screen. Like this, when the aspect ratio of the screen is made symmetrical, stereoscopic effect and the enlivening effect of the moving object is lessen. Accordingly, there is a need of a method of increasing the stereoscopic effect and the enlivening effect of the object moving in the image displayed on the screen.